The present invention relates to signal processing, and more particularly, to an operational amplifier based circuit with a compensation circuit block used for stability compensation.
With the advance of the wireless communications system, the baseband bandwidth becomes wider. Hence, a more stringent receiver (RX) requirement is needed by a broadband system such as an LTE-Advanced (LTE-A) system for ensuring the received signal quality. For example, to prevent noise figure (NF) degradation on the signal channel edge, a current-mode CR filter (e.g., low-pass filter) between a mixer and an operational amplifier based circuit (e.g., a transimpedance amplifier (TIA)) cannot be configured to filter out the blocker signal on the signal channel edge. If the current-mode CR filter is configured to filter out the blocker signal on the signal channel edge, the source impedance of the TIA is significantly reduced on the signal channel edge. However, the reduced source impedance of the TIA will result in increased noise in the output of the TIA, thus leading to NF degradation on the signal channel edge. Further, the operational amplifier implemented in the TIA needs to provide broadband input impedance as mixer's load to maintain mixer's linearity, and must have capability to sustain the blocker signal. Thus, there is a need for a wide-bandwidth and high-linearity operational amplifier based circuit with an innovative stability compensation design.